Japanese Patent Application Publication No. 2008-238792 discloses a liquid ejection device including a main body and an ink cartridge. The main body includes a liquid ejection head and a sub-tank. The ink cartridge has a liquid storage chamber and is detachably attachable to the main body. A sensor arm is provided in the liquid storage chamber. The sensor arm is pivotally moved when a liquid level of ink in the liquid storage chamber becomes equal to or less than a predetermined level. A residual amount detection sensor is provided in the main body. The residual amount detection sensor outputs detection signals different from each other depending on pivotally moving position of the sensor arm. A residual amount of ink in the liquid storage chamber is determined on a basis of the detection signal transmitted from the residual amount detection sensor. A message indicative of prompting replacement of the ink cartridge with a new cartridge is notified when the residual amount of ink in the liquid storage chamber becomes equal to or less than a predetermined amount in accordance with consumption of ink in the liquid storage chamber.